Low power system

[jana519]

Hello, I am building a low power system and need some input. This isn't my primary PC, it's more like an "experimental" build. I've already picked out the parts but I need help on minimizing the power consumption.

Parts:
LGA 1150 Core i5 "S" processor (65W)
2x4GB DDR3 RAM (1.35V)
Gigabyte GA-H81N or Asus H97i-Plus
128GB mSATA or m.2 drive
PicoPSU-160W-XT
GTX 750 Ti
Case (probably custom-made)
Windows 10

I want to undervolt the processor and I am not entirely sure the GA-H81N will allow me to do that. I'm pretty sure the H97i-Plus has manual voltage in BIOS, but it also has a larger VRM with more MOSFETs, chokes, and capacitors which I think use more power overall?

Another difference between the two is the GA-H61N has an mSATA port, but the H97i-Plus has an m.2 port.

Which motherboard is best for reducing power? Also what else can I do to make the peak power draw as low as possible?

 

[Yuriman]

Personally, I'd go socket 1151. DDR4 is lower voltage (1.2v), 14nm has superior power characteristics below maybe 3.8ghz, and the chipset itself is built on 22nm rather than 32nm. All Skylake non-K quad cores are 65w, not just the "S" models.

Another alternative is going with a Broadwell CPU. The iGPU might not be powerful enough for your needs and Intel's video drivers are, uh, limited, but in terms of performance per watt, you probably can't beat Broadwell.

You might get something out of my thread here:

http://forums.anandtech.com/showthread.php?t=2443083&highlight=

EDIT:

At stock frequency and undervolted (1.016v), my whole system draws 81.6w at the wall with Prime95 running...

^ Video card is not loaded, but it accounts for 12w of that power consumption just idling. GTX750 Ti should be a significant improvement over my relatively old 7850, both at idle and under load.

 

[jana519]

DDR4 is lower voltage (1.2v), 14nm has superior power characteristics below maybe 3.8ghz, and the chipset itself is built on 22nm rather than 32nm.

The three reviews I've found so far are all comparing their i7-6700K at 4.2 and 4.4 Ghz and that shows Skylake actually consuming more power than Sandy Bridge. If you could point me to some actual numbers about Skylake power consumption for the stock i5-6400/6500 that would be helpful.

 

[Yuriman]

Data are very scarce on non-K chips, but it can be inferred from benches on K CPUs.



This Hardwareluxx review shows the i5 6400 drawing less power than an i3 4130:

TomsHardware found that while the 6700K draws more power than the higher-clocked 4790K, the 6600K draws far less than the equally-clocked 4690K. This is suggestive of the idea that Skylake requires more power to hit higher frequencies, but less power at lower frequencies, with the crossover point being somewhere around 3.8-4ghz.

What Hexus found:

Note that in this review, when the 6700K is drawing more power, it is also still performing much higher than Haswell:

 

[jana519]

I like the Skylake idea, think I am going to move to that platform. Seems like a Skylake CPU can save 10W power over it's Haswell counterpart.

One thing I'm not sure about is what SKU I should get. I'm really considering the i5-6400T. There's an Amazon seller who has them for $154. The other "T" SKUs start at $220.

It seems like keeping the frequency lower could be a good idea. Debating either the i5-6400T, i5-6400, or i5-6500. Any recommendations?

 

[JeffMD]

Why are you looking to go the extra mile for power reduction, and what kind of power do you need? What will you be doing on the pc?

 

[jana519]

Why are you looking to go the extra mile for power reduction, and what kind of power do you need? What will you be doing on the pc?

Just a interest/obsession with form factor and how small I can go. The reason I'm so heavily interested in power draw is because a PicoPSU ATX-DC power supply is rated for 160W and I am trying to stay below that limit.

 

[LTC8K6]

Unless they are working hard, modern cpus just don't use much power.

But you can still see that Skylake has an advantage even at idle.

 

[nerp]

Skylake or bust. A PC is idle for most of its life. That's where the savings will come.

 

[JeffMD]

Just a interest/obsession with form factor and how small I can go. The reason I'm so heavily interested in power draw is because a PicoPSU ATX-DC power supply is rated for 160W and I am trying to stay below that limit.

You can always go smaller. Ive been impressed with the ULV processors. 15 watts.

 

[piasabird]

One thing about power consumption is other things matter as well.
One thing is the number of ports you keep active for things like SATA, USB, Printers, wireless networking (Power Hog), DVD, Hard drives, wireless keyboard, and any other things you might plug in like a microphone, speakers, camera.

So one way to approach this is to decide how many of what types of devices you want to use at maximum, and only get a motherboard with that number of connections. You could also go to newegg and look at embedded motherboards. If you are going to consider under-clocking why not get a CPU that is under-clocked already. The T CPU's are under-clocked so they make less heat. Of course using a video card would then defeat the purpose.

Some retail devices like the Intel NUC and Gigabyte Brix are probably using the u series CPU's. They may be a good option.